As the prior art concerning benzothiazone compounds which are useful for treating circulatory diseases, there exists the publication of European Patent Application (publication No. 116368) disclosing the compounds having 3-oxo-2H-1,4-benzothiazine as the main structure, which appears in the compounds of the present application.
However, such publication discloses only 2-mono substitutes and does not represent 2,2-disubstituted benzothiazine or benzothiazine derivatives having the substituent(s) at 5 to 8 position(s) as in the present application.
There was few studies on 2,2-disubstituted benzothiazine or benzothiazine derivatives having the substituent(s) at 5 to 8 position(s), so the necessity arose studing methods of synthesis and efficacy of such derivatives.
We synthesized a series of 2,2-disubstituted benzothiazine and benzothiazine derivatives having the substituent(s) at 5 to 8 position(s), and examined the efficacy thereof.